The present invention relates to a process, a method of, and an apparatus for transferring heat to food articles and, more particularly, to a novel process, method of and apparatus for such purpose, that are particularly adapted for either cooking from frozen or fresh state or for holding previously cooked food articles, equilibrated to a preferred, pathogenically safe internal temperature for prolonged time periods, and which can also be employed to initially cook food articles or to complete the cooking cycle for food articles that have previously been partially cooked, or are fresh-frozen and packaged for cooking in a plastic pouch, hermetically sealed and relatively free of oxygen for extension of the food article's shelf life in frozen format for periods of up to one year.
The multi-deck clamshell cooking and staging grill of the present invention utilizes conduction and radiation heat transfer dynamics relevant to low-temperature cooking and staging of non-cured meats, particularly ground red meats such as hamburger beef patties. Escherichia coli 0157:H7 and other pathogenic risks are reflected herein as a food safety risk management process and the apparatus to consistently and repetitiously achieve it.
In regard to retail mass feeding of commercial-level, grilled hamburger products, the bacteriological and pathogenic food safety, color, moisture content, and texture uniformity of the product is of primary concern to the ultimate consumer. The physical characteristics reflect the reference point of quality standards associated with this commodity meat product. Hamburger products which are cooked by high-heat, high-speed grilling processes are subject to considerable moisture weight losses during any cooking-grilling processes, and require stringent bacteriological safety monitoring.
It must be understood that the energy of heat (i.e., Btu's) can be transferred to any respective product by many different means, yet the key issue is always directly related to the optimum "efficiency factor" associated with any heat transfer processing technique, in this case from a heat source to a food article. The mass production of grilled hamburger products in the fast food service industry is presently accomplished via several conventionally practiced methods, such as the open grill or flame grill, both high-temperature grills utilized extensively worldwide each of which is either electrically or gas-fired.
Conventionally practiced grilling procedures rely on the heat transfer by conduction from a heated grill surface to the respective food article. From a technically descriptive, factual point of view, any plate surface that can be heated by whatever means (e.g., electrical, gas or circulated liquid heat transfer media) is considered to be rightfully designated as a "grill," irrespective of any specific operational surface temperature achievable by various temperature control means. In simple terms, any plate that can be heated to and controlled at an operationally safe temperature can legally be designated as a grill surface plate. Even a cold plate is considered a grill, if the plate is equipped with heating means to achieve a rise in grill surface temperature capable of achieving thereby a desired temperature transfer via a specific process objective to a food article, based on a specific time-temperature heat transfer curve.
The desired internal product temperature achievement, from either frozen or refrigerated food product state, depends therefore on the time span of the food article's exposure to the time span required to achieve a desired internal product temperature. This process, conventionally practiced, has been proven over many years of practice to steadily fail in guaranteeing the consistent, dependably reproducible achievement of a precise internal product temperature within the narrow range of .+-.2.degree. F., in the millions of product grilling cycles performed daily throughout the industry on a worldwide basis.
Thermal lethality (i.e., destruction) of pathogenic bacteria such as Escherichia coli 0157:H7 to a safety factor of 99.999% requires a precise time-temperature relationship, which must be consistently achieved with absolute perfection millions of times per day. The cross-sectional color profile of an uncured, cooked meat product, however, is, a function of temperature alone--time is an irrelevant factor. The cross-sectional "color" of a cooked meat patty (i.e., a grilled hamburger), therefore, is a function of the ultimate internal product temperature reached and maintained for the staging (i.e., holding) period. We demonstrate that the hemoglobin present in red meat is sensitive to color development only with respect to precise internal product temperature, and is therefore not dependent upon any certain of length of time during which the hamburger patty is exposed to precisely controlled (to within the narrow range of .+-.2.degree. F., at temperature variances from 150.degree. to 165.degree. F.), internal or external product temperatures commonly practiced in conventional cooking, grilling and staging processes.
It is therefore physically impossible to evaluate a cooked food product by its color and ensure that conventionally cooked (i.e., grilled) fast food hamburgers achieve exact, pathogenically safe, optimum internal temperatures within specific time spans due to uncontrollable hot and cold spots which are inherent shortcomings of conventional grills. Restaurants currently cook (i.e., grill) hamburgers, and then usually store (i.e., "hold" or "stage") them temporarily in various, high moisture-generating heating units developed by the industry for that function. The quality of products staged in such equipment deteriorates rapidly, due to degradation of the product in terms of moisture loss, declining flavor intensity, cosmetic appearance and "mouth feel," and, most importantly, uncontrollable pathogenic risk management affecting the food product's safety for consumption and resulting in an organoleptically stewed" meat profile.
The lower an end internal product temperature factor is achieved, the lighter the pink color will be maintained in the ground meat product's cross-section. Conversely, the higher the internal temperature of the product is elevated, the darker the meat patty's color will develop until, in due time, the product's cross-section turns grayish brown in color at the point of full doneness (in the range of 155.degree. to 165.degree. F.).
Since scientifically verified regulations were published by the USDA and FDA in the Federal Register in 1993, specifying mandatory guidelines and establishing a standard, precise time-temperature relationship for guaranteed thermal lethality of pathogenic organisms in uncured ground meat patties for the industry to implement and practice, it became evident that in practice, under "real world" conditions, these objectives and regulations cannot be consistently achieved via conventional grilling equipment and procedures as currently practiced in the industry worldwide.
Until quite recently (prior to 1991) thermal lethality (i.e., "thermal kill") directives for dangerous pathogens in food articles, published by the U.S. Department of Agriculture [hereinafter "USDA"], required that a ground beef patty be thermalized (i.e., cooked) on a grill to an internal temperature of at least 145.degree. F., and then maintained at a 145.degree. F. internal temperature for staging (i.e., "holding hot" storage). Due to the subsequent discovery of increased heat resistance of lethal pathogens in food products, as revealed during ongoing, extensive research by the federal authorities to clearly identify public health hazards, in 1993 the USDA and the U.S. Food and Drug Administration [hereinafter "FDA"] dramatically increased their directives' internal food cooking temperature mandates in order to assure public food safety in accordance with the time- and temperature-related cooking requirements represented by Table I and Table II, and mandated into compliance law as published in the Federal Register.
Table I shows the Time-Temperature Cooking Requirements As Mandated by the USDA prior To 1991. The data for Table I is shown for the time/temperature combination for cooked ground beef, cooked beef, roast beef, and cooked corned beef as follows:
TABLE I ______________________________________ Minimum processing time in Minimum internal temperature minutes after minimum temperature (Degrees Fahrenheit) is reached ______________________________________ 130 121 131 97 132 77 133 62 134 47 135 37 136 32 137 24 138 19 139 15 140 12 141 10 142 8 143 6 144 5 145 Instantly ______________________________________
Table II shows the Time-Temperature Cooking Requirements As published by the USDA in 1993. The data for Table II is also shown for the time/temperature combination for cooked beef, roast beef, and cooked ground beef as follows:
TABLE II ______________________________________ Minimum processing time after Minimum internal temperature minimum temperature is reached (Degrees Fahrenheit) (Seconds) ______________________________________ 151 41 152 32 153 26 154 20 155 16 156 13 157 10 158 7 159 4 160 1 ______________________________________
Based on these recently recognized facts the issue of precise and repetitiously consistent, internal product temperature control, in relation to product staging (i.e., holding) time, becomes the single most critical factor in the attempt to guarantee both bacteriological (i.e., pathogenic) product safety, as well as a consistently high level of end product first quality attributes, which are dependent on the maximum retention of moisture in the meat patty, by which organoleptic product quality attributes are subconsciously measured for reference by the consuming public.
Thus, regardless of the specific cooking (i.e., grilling) technology deployed in processing hamburger products, via either conduction heat, convection heat or steam heat, also known as "wet cooking," the precise and consistent internal product temperature control factor, to be attained and maintained according to USDA regulations in each beef patty unit irrespective of minute, individual weight variances existing in the total batch, is the single most critical quality control factor affecting the food safety, optimum yield (i.e., moisture retention) and uniform doneness specifications of the end product, replicable millions of times per day absent any reliance on human judgment and without the danger of potential human error jeopardizing food safety.
If grilling temperatures higher than the ultimately desired internal product temperature of 155.degree. to 165.degree. F. are utilized during a cook cycle, then, regardless of the specific grilling heat source, the desired internal product temperature of each individual beef patty will be reached at time and temperature variations directly related to differences in unit weight, mass, and moisture and fat percentages. Consequently patties with relatively lower single-unit weights, when exposed to elevated grill temperatures ranging from 350.degree. up to 425.degree. F., depending on the cooking methodology utilized, will attain higher internal temperatures within the same given time span than will those patties with greater unit weights.
It is emphasized that precise control of individual unit weight factors in mass produced, ground meat patties, to within a variance of less than .+-.0.01 to 0.0125 grams per single product unit, is economically unfeasible. Any attempt to further narrow this weight tolerance per single ground meat patty unit is not justified, as such would increase the product's end price on the marketplace above a competitive "commodity" level.
Consequently, the only option available to precisely control the internal temperatures of individual ground meat patty product cooked (i.e., grilled), in small or large batches, irrespective of their variable single unit product weight factors, is by exposure of the total volume of products to a conduction heat transfer environment maintained precisely at, and not higher than, the end temperature d&sired as the ultimate internal product temperature for the entire batch. Under these conditions all single patties, regardless of their variable unit weights, will ultimately equilibrate at an identical internal product temperature, within the narrow range of .+-.1.degree. F., within a given time span, thereby meeting all USDA regulations related to time-temperature exposure and consequently guaranteeing bacteriological safety and optimum end product quality attributes.
Thus, the product unit with the least unit weight factor will reach a given internal temperature of, as an example, 150.degree. F., if exposed to a conduction temperature of 150.degree. F. for a time factor of X; where units with greater unit weight factors will ultimately attain the identical internal temperature with a time factor of X+Y, while the smaller product unit is simultaneously maintained (i.e., held) at the ultimate temperature during the time span required for larger product units to reach optimum internal temperature as specified in the USDA's mandatory regulations.
No single grilled product unit, however, regardless of its variable individual weight factor, will ever attain a higher equilibrated internal temperature than the conduction temperature to which the full batch is exposed, in the above example 150.degree. F. Bearing in mind the objective of such precise internal temperature control over products varying in their respective unit weights, the time span utilized to equilibrate and hold is therefore dependent on the specific grill surface conduction temperature exposure, and demonstrates the consistent achievement of control over the most critical point of reference of the process and apparatus.
Conventional methods for temporary storage or staging of hamburger patties in high-humidity environments for prolonged time spans does affect the product's optimum yield (i.e., moisture content), tenderness and myosin bond structure, thereby influencing the patties' organoleptic attributes as well as their perceived "bite-feel."
The multi-deck clamshell, low-temperature conduction and radiation, cooking and staging grill of the present invention may be used as a means of thawing precooked, frozen meat patties, cooking fresh-frozen meat patties, or staging for equilibration purposes, with the advantage of fully grilled patties consistently achieving equilibrated internal product temperatures varying between 145.degree. and 165.degree. F., within the narrow, selectable temperature range of .+-.1.degree. F. The meat product processed thereby retains a significantly higher moisture content than during the high-speed elevation of internal product temperature by conduction through exposure to surface grill temperatures ranging from 350.degree. to 425.degree. F. The multi-deck cooking and staging grill is designed for maintaining internal product temperature equilibration to a final, pathogenically safe temperature, requiring only that the sum total of all products exposed to the equilibration process in the staging grill to achieve a temperature equilibration balance between 1.degree. and 15.degree. F. A maximum temperature elevation of only 10.degree. to 15.degree. F. is needed to raise all individual food articles to the ideal internal temperature when these products have been either fully cooked on an open grill or a clamshell grill at high speeds, for between 90 and 240 seconds, as practiced universally by the industry with high-speed, high-temperature grills.
Based on the above-described critical factors associated with the mass production of grilled ground beef (i.e., hamburger) products, the optimum risk management via the low-temperature clamshell cooking and staging grill technology offers the most precise and efficient heat transfer dynamics capable of consistently guaranteeing the bacteriological (i.e., pathogenic food) safety, color uniformity, moisture retention and highest organoleptic quality attributes in the mass production of this food article, all benefiting the perfection of state-of-the-art technical performance achievements for providing first quality food which is impossible to attain with conventionally known and practiced grilling technologies.
Ground red meats which are neither injected nor marinated with curing agents of any type, such as nitrites, nitrates, salts, phosphates or other formulated curing agents, may be subjected to various internal product temperature elevation procedures resulting in desired doneness levels (i.e., cross-sectional color intensity, from bloody pink to grayish brown), ranging from 130.degree. to 165.degree. F. in temperature exposure. The meats are then held at a selected, precise temperature for various staging time spans in accordance with stringent USDA regulations depending strictly on exposure to their specific temperature factors for desired, uniform cross-sectional color profile development. Contrary to conventional grilling processes, the actual staging (i.e., holding) time factor, at an equilibrating temperature from 150.degree. to 165.degree. F., is therefore irrelevant in determining the cross-sectional meat color profile.
The preferred embodiment of the multi-deck, low-temperature conduction and radiation, high-speed cooking and staging grill comprises at least one and preferably a plurality of horizontally hinged, layered, and interlocking trays forming "decks" in a clamshell arrangement. Each tray, or plate, comprises a first and second sheet, having a serpentine fluid heat transfer passage formed thereinbetween for recirculation of a heat transfer media. The recirculated heat transfer media and the surface of the plates are precision-controlled within the narrow range of .+-.2.degree. F. at selected "low" temperatures up to 205.degree. F., or higher when temperatures up to 500.degree. F. are desirable. The trays are designed to effect uniform, low-temperature conduction and radiation heat transfer to the center of each patty or other food article. A computerized, electronic control system directs and monitors the process, and records the time and temperature variables, as well as ultimate internal product temperature equilibration, for the multi-deck cooking and staging grill.
The multi-deck cooking and staging grill, in either single-, double- or multi-deck format, will provide equilibrated temperatures for any selected conductive grill surface within the center of each ground beef patty within the precision of .+-.1.degree. F., irrespective of the position of the patty on the grill plate, or weight, thickness or circumference variables of a wide variety of meet patties. Once a single hamburger (or multitude of patties) is placed in the grill's trays, and clamped between two conductive grill plates from the top and bottom, the equilibration temperature selected to effect thermal kill of trace pathogens will be maintained for a minimum time span, as mandated by federal regulations to be sufficient to kill any pathogenic bacteria, before the tray can be opened and the product served. A computerized electronic process monitoring means signals (both audibly and visually) when a tray of hamburgers is available for dispensing and safe consumption, thereby meeting USDA- and FDA-mandated pathogenic thermal lethality requirements for cooked food articles.
Furthermore, the multi-deck clamshell cooking and staging grill is designed to incorporate interlocking, stacked trays in various shapes and sizes, formed as to depth into a "pan" means, wherein the bottom, deep-drawn "pan tray" is constantly heated by conduction, via the hot, circulating heat transfer fluid, thereby cooking and "holding hot" any food product that is maintained in unit form or in bulk, in an absolutely safe and perfect temperature environment between 160.degree. and 205.degree. F., depending on the specific ideal, or preferred, temperature of any specified food article. The heated, "deep pan tray" is covered with the bottom of a heated plate, positioned above the heated deep pan tray, thereby forming a "lid" means which can be elevated to offer easy removal of a product from the lower deep pan tray for hot food serving purposes at high speeds, and instant lid closure for maximum uniform heat retention of the stored hot food in the bottom pan.
All vertical, perpendicular and horizontal, fluid-connected vessels will be connectable and disconnectable from the recirculating liquid heat transfer hot media supply via standard, quick-disconnect means, which are available for this application from several manufacturing sources. The same process principle can be practiced in a variety of shapes and apparatus configurations such as double-walled vessels for maintenance of hot soups, coffee, tea, and other foods constituting liquid and solid food substances.
The method and apparatus described herein for the multi-deck, conduction and radiation, clamshell cooking and staging grill and processing procedures have a significant impact on the quality of the cooked, hot food product during prolonged staging, due to the fact that any product subjected to this unique staging (i.e., hot holding) procedure will have a dramatic, time-related quality and food safety elasticity by at least 100 to 300 or more percent longer, due to its higher moisture content retention achieved by the precision equilibration internal and external food article temperature control and the environment in which the food is stored, by convective, conductive and radiation equilibration within the narrow range of .+-.2.degree. F., for hours of safe maintenance, without generating any excessive water vapor (i.e., moisture evacuation) from the hot-held food article of protein or farinaceous composition.
The net result is not only addressing the achievement of bacteriological and pathogenic food safety, but highlighting the retention of the delicate, volatile, "seared" flavor components achieved during the preliminary, high-temperature grilling process, and by avoiding the subjection of previously grilled food products to a high-moisture (i.e., saturated) environment in secondary staging which will, by rapid oxidation, negatively quench and dissipate the delicate aromatic and flavor components and preferred attributes achieved with high-temperature grilling, which are organoleptic quality attributes most desired by the consuming public.